Changes to the natural environment

The 2010-2011 Canterbury earthquakes, and to a lesser extent, the 2016 Kaikōura-Hurunui earthquake, caused uplift and subsidence of land in Southshore, South New Brighton and in the Estuary/Ihutai; as well as liquefaction, lateral spread and other effects of ground shaking. This led to changes in the ground surface, physical processes, and ecosystems.


What we know

Estuary bed tilt

The earthquakes caused the bed of the Estuary/Ihutai to tilt, lifting in the south and subsiding in the north - particularly near the mouth of the Ōtākaro/Avon River, north of Bridge Street. The tilting has altered drainage and inter-tidal water levels within the Estuary/Ihutai.


Ground elevation change following the Canterbury earthquakes. Difference between 2003 LiDAR survey undertaken by Christchurch City Council and 2012 LiDar survey undertaken by EQC.


Changes in ground levels in the Regeneration Strategy project area

Post-earthquake surveys of ground elevation indicate that the Regeneration Strategy project area has experienced subsidence and uplift in both the 2010-2011 Canterbury Earthquakes, and the 2016 Kaikōura-Hurunui earthquake.


Changing ecosystems

There has been small areas of both loss and migration of saltmarsh due to subsidence and tilting of the estuary bed.

Liquefaction within the Estuary/Ihutai presented as ‘sand volcanoes’ caused a change of grain size distribution of the sediments in the Estuary/Ihutai . However, the grain size distribution of the sediments at monitoring sites within the Estuary/Ihutai is returning to pre-earthquake conditions. As previously mentioned, sewage discharges into the rivers and the Estuary/Ihutai affected water quality in the short term.


Why this is important

Changes in the Estuary/Ihutai mouth, channels and shoreline are likely to continue as the water flowing in an out of the Estuary/Ihutai adjusts to the altered bed.

Depending on the location, changes in ground levels may change the susceptibility to natural hazards such as shallow groundwater or flooding. Here is some more information about natural hazards.


What we don’t know

It is not clear at this stage how the landform changes in the Estuary/Ihutai bed, the Estuary/Ihutai mouth, and the surrounding land will affect coastal processes in the long-term, and what the implications of any changes will be.

The 2010-2011 Canterbury earthquakes, and to a lesser extent, the 2016 Kaikōura-Hurunui earthquake, caused uplift and subsidence of land in Southshore, South New Brighton and in the Estuary/Ihutai; as well as liquefaction, lateral spread and other effects of ground shaking. This led to changes in the ground surface, physical processes, and ecosystems.


What we know

Estuary bed tilt

The earthquakes caused the bed of the Estuary/Ihutai to tilt, lifting in the south and subsiding in the north - particularly near the mouth of the Ōtākaro/Avon River, north of Bridge Street. The tilting has altered drainage and inter-tidal water levels within the Estuary/Ihutai.


Ground elevation change following the Canterbury earthquakes. Difference between 2003 LiDAR survey undertaken by Christchurch City Council and 2012 LiDar survey undertaken by EQC.


Changes in ground levels in the Regeneration Strategy project area

Post-earthquake surveys of ground elevation indicate that the Regeneration Strategy project area has experienced subsidence and uplift in both the 2010-2011 Canterbury Earthquakes, and the 2016 Kaikōura-Hurunui earthquake.


Changing ecosystems

There has been small areas of both loss and migration of saltmarsh due to subsidence and tilting of the estuary bed.

Liquefaction within the Estuary/Ihutai presented as ‘sand volcanoes’ caused a change of grain size distribution of the sediments in the Estuary/Ihutai . However, the grain size distribution of the sediments at monitoring sites within the Estuary/Ihutai is returning to pre-earthquake conditions. As previously mentioned, sewage discharges into the rivers and the Estuary/Ihutai affected water quality in the short term.


Why this is important

Changes in the Estuary/Ihutai mouth, channels and shoreline are likely to continue as the water flowing in an out of the Estuary/Ihutai adjusts to the altered bed.

Depending on the location, changes in ground levels may change the susceptibility to natural hazards such as shallow groundwater or flooding. Here is some more information about natural hazards.


What we don’t know

It is not clear at this stage how the landform changes in the Estuary/Ihutai bed, the Estuary/Ihutai mouth, and the surrounding land will affect coastal processes in the long-term, and what the implications of any changes will be.